The present invention relates to the installation of cross-country pipelines, conduits, cables, and the like, and more particularly to their installation under a barrier.
Pipeline must be installed under barriers such as highways, waterways, buildings and other surface obstructions without disturbing the surface. Typically this has been done through a coring or boring process. For example, when an interstate highway is encountered by a pipeline, a trench is opened on either side of the highway. A boring apparatus is placed on one side of the highway and a passageway is formed under the highway between the two open trenches. The bore is of sufficient size to allow a section of pipe to be pushed lengthwise through the bore from one side of the highway to the other. The installed section is then welded into the pipeline and tested.
When rock or other hard materials are encountered in the boring operation, problems can arise which cause the installation to be difficult and expensive. For example, when installing a 36" or 40" pipeline under a 300' wide interstate highway, massive forces can be present during the process of inserting the pipe in the bore. This can be caused by the fact that when hard materials are encountered by a large boring apparatus it is difficult, if not impossible to form the bore in a straight path. When rock or other hard materials are encountered the cutter can tend to corkscrew, bend and deviate from a straight path. This causes installation of straight pipe to be difficult, if not impossible. In some cases the pipe will become stuck during the process of insertion into the bore. The stuck pipe must be cut and the bore filled up and a new bore formed. These and other difficulties in boring through barriers of rock or other hard materials for large pipelines cause the process to be difficult and expensive.